EP3285963A1

EP3285963A1 - Method for the complete grinding of workpieces in the form of shafts having cylindrical and profiled sections

Info

Publication number: EP3285963A1
Application number: EP17708519.8A
Authority: EP
Inventors: Erwin Junker
Original assignee: Erwin Junker Maschinenfabrik GmbH
Current assignee: Erwin Junker Maschinenfabrik GmbH
Priority date: 2016-03-15
Filing date: 2017-03-03
Publication date: 2018-02-28
Anticipated expiration: 2037-03-03
Also published as: DE102016204273A1; JP6917904B2; JP2019509178A; EP3285963B1; RU2017140448A; ES2699329T3; ES2699329T5; WO2017157698A1; KR20180122269A; DE102016204273B4; EP3285963B2; BR112017022922A2; US10576602B2; RU2711392C2; CN107708925A; RU2017140448A3; KR102279986B1; CA2985411A1; US20180369983A1

Abstract

A method is disclosed for grinding workpieces having at least one cylindrical section and one profiled section on a single grinding machine. In a first set-up, the workpiece is first ground in the grinding machine during a first grounding operation, which is followed by a second grounding operation after the first set-up has been undone and a second set-up has been generated before the second grinding operation begins.

Description

METHOD FOR GRINDING COMPLETE MACHINING OF WAVE-SHAPED WORKPIECES WITH CYLINDRICAL AND PROFILEED SECTIONS

The invention relates to a method for grinding wavy workpieces having at least one respective cylindrical and profiled section on one and the same grinding machine as complete machining.

In the context of this invention, wave-shaped workpieces are understood to mean, for example, gear shafts, rotors for hydraulic pumps or flow meters, rotors for vane pumps and rotors for, for example, compressors for compressors, blowers, vacuum pumps or similar applications. However, the invention described below is also to be used in the sense of a broad interpretation of the term wavy workpieces on other shaft parts such as camshafts, crankshafts, etc. application. In known methods for grinding complete machining of corrugated workpieces with cylindrical and profiled sections, as is the case for example with gear shafts, the required recesses, facing sides and diameters are generally ground in separate work sequences and often also in a machine. By contrast, the profile sections or toothings likewise to be ground on the wave-shaped workpieces are ground on separate machines. The use of several machines, which are frequently arranged one behind the other in the production process, requires a high investment in machine tools and additional space requirements in the production halls. This also applies to rotor parts, which have cylindrical and profile sections and are ground in a similar manner for the various applications.

However, it is already known to grind wavy workpieces with cylindrical and profile sections on a machine. As a rule, the grinding of the cylindrical sections also includes the grinding of flat shoulder surfaces, which are present, for example, between adjacent cylindrical outer surfaces of different diameters. DE 199 21 785 B4 discloses a method for grinding convex running surfaces and outside diameters on shafts with at least one disk-shaped shaft cut and a corresponding grinding machine for performing the method known. The shaft part to be ground is to be ground in terms of a complete machining both with respect to the cylindrical portion or the cylindrical portions and the profile sections. The profile sections are described in these methods according to the embodiment described there as a disc-shaped shaft portion with a convex curved surface. Such convexly curved surfaces represent profile sections. The known method is now directed to that all grinding operations, ie a grinding operation for grinding the convex face-side running surfaces on the disk-shaped shaft section and a second grinding operation for grinding the respective desired outer diameter or cylindrical sections of the Shaft parts are ground in one clamping. This means that during the entire grinding process, the workpiece remains clamped at least between points between a workpiece headstock and a tailstock. This clamping is not solved during the entire processing.

WO 2012/100 307 A8 describes such a method for complete grinding of wavy workpieces with cylindrical and profiled sections, wherein the profiled sections are helically shaped profiles for rotors of, for example, compressors. In this known method, the workpiece also remains firmly clamped during the entire processing, so that the clamping is not released. Regardless of how many grinding operations are performed in terms of pre-grinding, finish grinding, grinding a steady seat, grinding the cylindrical sections, etc., the clamping of the workpiece is performed at the beginning of the grinding process, and the workpiece remains in this clamping during the entire grinding process curious; excited.

This also corresponds to the technical knowledge that is generally known today, according to which the workpieces are ground on a machine in a single setting in order to achieve tighter tolerances and improved shape and position characteristics. The known expertise currently assumes that at each re-tension manufacturing quality losses due to possibly occurring Umspannfehler are present.

From DE 10 2010 005 630 A1, the basic technical structure of a machine is described, with which a machining of wave-shaped workpieces according to the previously appreciated WO 2012/100 307 A8 can take place. In this known grinding center is indeed described above all, that in addition a storage magazine to be arranged for the respective grinding wheels required cooling nozzles or cooling nozzle sets In the grinding complete machining carried out by means of this known grinding center, the workpiece can also be completely clamped.

In contrast, the object of the invention is to increase the manufacturing accuracy of such complex components as the wavy wavy workpieces with cylindrical and profiled sections to be ground here.

This object is achieved by a method having the features according to claim 1.

Expedient developments are defined by the dependent claims.

According to the method according to the invention for grinding workpieces having at least one respective cylindrical and profiled section, such complete machining takes place on one and the same grinding machine. In this case, the workpiece is ground in the grinding machine in a first clamping operation in a first grinding operation and then ground in a second grinding operation, after the first clamping has been released and then a second clamping of the workpiece has been generated.

This procedure according to the invention, namely in which the taking place on the same machine clamping between individual grinding operations, namely without the workpiece must be removed from the processing station, specifically solved and then the workpiece for its further processing is firmly clamped, as a rule with the same clamping devices. Contrary to prevailing opinion in accordance with the knowledge of one of ordinary skill in the art, it has surprisingly been found that with such an approach, in which the clamping is consciously and selectively released between the individual grinding operations, further improved manufacturing qualities of the workpiece after grinding, in particular with respect to grinding on the dimensional, shape and position tolerances can be achieved. This depends u. a. together with that in the processing of workpieces z. B. at different Schleifaufmaßen during the cutting process, a different heat development. This varying cutting heat can lead to different thermal expansions or distortions on the workpiece, which can be compensated by an intermediate relaxation of the clamping.

Another reason is that in the manufacture of the green workpiece different residual stresses in the material are or remain, especially if these workpieces are still subjected to special heat treatments such as hardening prior to grinding. In such a case, even slight differences within the permissible technical tolerances in the green workpiece from different batches in the production come to Wear, since with the individual batches the heat treatment conditions can not be kept 100% constant from batch to batch.

Another reason for residual stresses in the workpiece can result from, for example, scrap material also being used in the production of the raw material or the green workpiece, which is still within the allowable technical tolerances for the green workpiece or the blank, but for subsequent ones Processing steps can lead to additional stresses and related deformations of the workpiece.

In the case of the manufacturers of the wave-shaped workpieces with cylindrical and profile sections considered here, it is also common for the materials for the green workpieces to be procured with the same specification from different manufacturers, often even from different countries. Even if the specifications are the same, the workpieces in the case of the sharpening process sometimes behave quite differently, in particular due to the release of residual stresses. This problem of the inherent stresses released from the material structure during processing inevitably leads to the finished workpieces having deviations in their dimensional, geometrical and positional tolerances despite otherwise constant grinding process parameters. Fluctuations in the dimensions in the m range down to the hundredth mm range are quite possible and customary. In particular, for rotor shafts, which are installed in screw rotors and must mesh very closely with each other as a pair of male and female rotor shaft, such fluctuations are unacceptable, low-wear operation, a corresponding seal when rolling the profiles and the like can be ensured. But also the temperature difference of the raw parts, which are fed to the grinding machine, exerts an influence on the accuracy. Here, for example, the differences in the temperatures of the workpieces supplied to the machine and the temperatures in the interior of the processing machine partially in no longer negligible effect. These temperature differences are all the more pronounced, the more pronounced the fluctuating blank temperature of the workpieces that are supplied to the processing machine, are.

Another important point that is important in achieving extremely high accuracy of such components is the type of pre-machining. Thus, the blanks or green workpieces can be designed in such a way that the grooves or teeth of the profile sections are already pre-machined by milling or other machining processes. In castings or forgings, it is sometimes possible with larger grooves or teeth that the grooves are already pre-cast or forged in their basic form, in In which case they have a higher grinding allowance than at z. B. have already milled grooves or teeth when they are fed to the grinding machine. Since the so-called casting skin is sanded off during grinding, the risk of loosening stresses during grinding is particularly high there, since the inner skin loses its internal stresses when the casting skin is sanded. By avoiding all the aforementioned disadvantages, it is possible to once again significantly improve the production quality. The improved manufacturing quality results from the fact that by the interim release of the clamping, which otherwise takes place so that the positioning of the workpiece is maintained in the grinding machine, the distortion of the workpiece due to the above reasons in the processing by the grinding so to speak "after This means that the workpiece can relax in the meantime when releasing the tension, so that it can be sanded again on a relaxed and firmly clamped workpiece during subsequent grinding operations In particular, this relates in particular to the stresses on the surface of the workpiece at the points where grinding takes place if machining an at least largely stress-free workpiece just then be processed more accurately. In general, the workpieces are first clamped in the machine, the

Workpieces are firmly clamped in the machine between the tips, as is commonly known in the art. In order to be able to grind the profiled areas of the grooves or toothings, the workpiece also has to be clamped radially free of play. This is preferably realized by a so-called compensating chuck. In these chucks, the workpiece is centered by the point in the chuck, and the

Clamping jaws rest in the state clamped between the tips of the workpiece spindle and tailstock, balancing the workpiece with its diameter, the tension force applied by this tension compensating and radially stiff the workpiece, d. H. play-free, tense.

In order to be able to drive the workpiece in a program-controlled, targeted manner during machining, the chuck is permanently mounted on a workpiece spindle, whereby the rotation drive takes place about the so-called C-axis. In order to be able to grind also the shaft end at which the chuck clamps the workpiece, this or the clamping jaws can be retracted in the opened state. Thus, the workpiece at the shaft end is free, so that the clamping diameter can also be ground. Here, the workpiece is clamped only between the centering. The friction between the driven Centering tip and the center in the workpiece transmits the torque required for grinding to the rotation of the workpiece. The workpiece to be ground is clamped during the grinding process in such a way that it is clamped between the tips and for the radial entrainment by the chuck is still stretched tightly compensating. Since the shaft parts generally have such a diameter-length ratio that they must be supported during machining, preferably a Lünet- seat seat is first sanded on the workpiece. However, this is only necessary if the diameter-length ratio requires additional support.

According to a first embodiment, the grinding of the diameters and the faces is preferably carried out with a grinding wheel, which is designed for peeling grinding. The cylindrical section on the workpiece is preferably made with a first, not cylindrical grinding wheel by a longitudinal peel grinding. The profiled section is made by profile grinding with a second, profiled grinding wheel. For the grinding of the diameter and sides of the planing the grinding wheel is preferably dressed so that the so-called gate of the grinding wheel is dressed at an angle. The main cutting during peeling grinding takes place in the short, conically dressed area of the grinding wheel. The outer diameter of the grinding wheel cuts relatively small, d. H. its surface is only used for smoothing the surface. With such a grinding wheel can also be ground flat. When the center axis of the grinding wheel is parallel to the axis with respect to the center axis of the workpiece, a so-called beam cut remains on the ground surface during the grinding of plan sides. Since this beam grinding is often undesirable, it is also preferable to ground the corresponding workpiece on its diameters and sides of the plan with an inclined grinding wheel. The grinding of the diameter ranges is also performed in the peel grinding process. The grinding of the plan sides is then ground with the obliquely dressed side surface of the grinding wheel in Schrägeinstechschleifverfahren. Preferably, however, it is also possible to grind a plurality of diameters in one or more plunge grinding operations at the same time or in succession with a wider grinding wheel, which is suitable for Schrägeinstechschleifen. In such a case, the grinding of the plan sides is also done with the obliquely dressed side surface of the grinding wheel.

Preferably, the first grinding wheel is arranged on a first wheelhead, and the second wheel is further preferably mounted on a second wheelhead. assigns. The advantage of having separate grinding headstocks for the first grinding wheel and for the second grinding wheel is that there is more flexibility in grinding. In the presence of two grinding headstocks and their arrangement on both sides of the workpiece, it is also possible to process certain sections on the workpiece at least partially in parallel with time. In the case of parallel machining of corresponding areas on the workpiece and arrangement of the grinding headstocks on both sides of the workpiece, it can also be achieved that the grinding forces imposed on the workpiece during grinding by the one grinding wheel are at least to a considerable extent compensated by the other grinding wheel.

According to one embodiment, the workpiece is clamped between points, which are introduced in the end sides of the workpiece and define its longitudinal axis. One of the tips is located on the tailstock and the other tip is located on the workpiece headstock. In the first set-up, the tip on the tailstock exerts a corresponding clamping pressure by means of an axially directed pressure load which is sufficiently high at least for the grinding of the cylindrical sections and / or the plan sides. The tail located on the tailstock can be converted from a state in which the axially directed pressure load is exerted on the workpiece to release the clamping in a pressure-free state. In such a non-pressurized state, the tip on the tailstock still engages the centering bore on the workpiece on the side of the workpiece facing the tailstock, thus ensuring the alignment of the workpiece on the longitudinal axis of the workpiece defined by the centering bores. The unpressurized condition of the tip on the tailstock gives the workpiece the possibility of compensating certain internal stresses released during grinding, so that for the next grinding operation, when the clamping is repeated, the workpiece can be ground largely free of internal stress.

To release the clamping, ie for pressure release of the tip on the tailstock the tailstock tip is moved along its Z-axis. As a result, it is, as it were, out of engagement with the centering bore of the workpiece facing the tailstock tip. Under "disengaged is understood in this context, the non-pressurized state of the centering in the center hole of the workpiece, in which a rotary drive on the clamping between the tips for the workpiece is no longer possible. When grinding the profile sections usually higher grinding forces occur, which are introduced by the respective grinding wheel in the workpiece. In order now to prevent that in the sole clamping of the workpiece between peaks in the relatively large Abrasive forces when grinding the profile sections, the friction forces at the top of the workpiece headstock for rotation of the workpiece may not be sufficient reliable, an additional clamping device is provided on the workpiece headstock, which additionally biases the workpiece on the outer circumference of a cylindrical portion. Preferably, the additional clamping device biases the workpiece with its engaging on the circumference of the workpiece clamping jaws. If a loosening of the first clamping is now carried out between individual grinding operations during profile grinding, for example between the profile roughing and finish grinding of the profile, the clamping device is also for the purpose of completely relaxing the workpiece, ie for compensating its internal stresses released during grinding to be released when the tip on the tailstock is depressurized.

In particular, in the case of longer workpieces, at least one steady rest seat is ground in the first slide operation, and thereafter, in the second grinding operation, the profiled section is pre-ground. In a third grinding operation, the cylindrical portion and the plane surfaces present on the workpiece are then ground, followed by the finish grinding of the profiled portion in a fourth grinding operation. Preferably, the clamping is released in each case between all successive grinding operations and then the workpiece is tensioned again before the respective subsequent grinding operation begins.

After the finish grinding of the steady rest seat, a bezel for supporting the workpiece is preferably employed at this Lünettensitz after it has been ground. The support by means of a steady rest is above all advantageous when grinding operations are carried out with longer workpieces, in which only one grinding wheel is engaged with the workpiece. The grinding of the steady seat represents the first processing step during which the workpiece is clamped firmly in the machine, i. H. is in the first setup. After grinding the Lünettensitzes then further diameter be pre-ground with any plan surfaces therebetween or even finish ground. Depending on the workpiece geometry, the grinding of the diameters also includes the grinding of plane surfaces connecting the individual diameter ranges of different diameters.

The present invention is based on the idea that, by releasing the clamping between successive grinding operations while simultaneously ensuring the holding of the workpiece to be ground on the spindle headstock and the tailstock, as well as the centering holes present in the end faces of the workpiece. ments defined longitudinal axis internal stresses are reduced, which longitudinal axis represents the referenced reference axis for grinding. In subsequent grinding operations on the workpiece can then be ground free of such internal stresses or at least significantly reduced internal stresses. The subsequent subsequent loosening of the clamping further loops in the presence of a substantially internal tension inside the workpiece in any case leads to improved grinding results, and contrary to the prevailing opinion, according to which the workpiece as far as possible during the entire grinding operations and without intermediate release of the clamping should be kept in this setup.

The release of the tail stick side can also be done in such a way that the tip is withdrawn by a certain amount, d. H. no longer in the center. Here, the workpiece will then rest on so-called Vorabiageprismen in this state and then clamped again. By this procedure, the same technical effect as in the procedure described above is achieved.

Further advantages and embodiments of the method according to the invention will now be described in detail in the following figures. In the drawing: FIG. 1 shows a top view of a grinding machine for carrying out the invention

Method with a wheelhead and a station for clamping a workpiece; a plan view of a grinding machine for carrying out the method according to the invention with two grinding head and a station for clamping a workpiece; a partial top view of a clamped for performing the method according to the invention between peaks workpiece before the beginning of the grinding of a Lü- seat;

FIG. 4A: a partial plan view according to FIG. 3 during pre-grinding of the profile section in the form of a toothing or grooves with supporting steady rest; FIG. 4B: a partial view in the direction A of the workpiece according to FIG. 4A during the FIG

Grinding its profile section; FIG. 4C shows a partial sectional view BB according to FIG. 4B during the grinding of the profile section of the workpiece designed as a straight longitudinal groove;

FIG. 5 shows a partial plan view according to FIG. 3 during finish grinding of the centric diameter and the plan sides of the workpiece according to the method according to the invention;

FIG. 6: a partial top view according to FIG. 3 during finish grinding of the toothing or the

Grooves of the workpiece according to the method of the invention; and

FIG. 7: Examples of workpieces which can be sanded with the method according to the invention with cylindrical, shoulder shoulder and profile sections.

FIG. 1 shows a plan view of a grinding machine for carrying out the method according to the invention, in which a workpiece is clamped in such a way that it makes it possible to carry out the method according to the invention for complete grinding of undulating workpieces or shaft parts 10. The grinding machine shown in plan view has as a grinding center on a machine stand 1, a arranged on the machine frame 1 workpiece spindle support 2 with CNC-controlled C-axis and a tailstock 3 on. Between the workpiece spindle holder 2 and the tailstock 3, the workpiece, not shown, is clamped so that its geometric longitudinal axis coincides with the clamping and rotation axis 4. A cross slide is parallel, which is indicated by the double arrow marked as Z-axis, and at right angles, which is indicated by the designated as X-axis further double arrow, to the axis of rotation 4 of the workpiece CNC-controlled movable. The cross slide carries over vertical guideways 19, CNC-controlled movable, which is represented by the also indicated as a double arrow Y-axis, a first wheelhead 5, to which a grinding spindle 9 is fixed with a grinding wheel 11. Another CNC-controlled adjustment consists of a horizontal, perpendicular to the axis of rotation 4 of the workpiece arranged CNC-controlled pivot axis 12, which is marked and shown as A-axis.

In order that grinding wheels can be used in the Schrägeinstechschleifverfahren for grinding cylindrical or conical portions of the shaft portion, a pivot axis is preferably provided above the carriage for the Z-axis, which has a vertically arranged pivot axis 13 and is designated in Figure 2 as a B-axis. In Figure 1 this is

Swivel axis not shown, as they only for grinding with inclined grinding wheel 11 is required for peel grinding or bevel grinding. This means that it can be ground in the Schräginstechschleifverfahren, or it can also cones are ground by pivoting the B-axis. If this B-axis, ie the pivot axis 13, does not exist, it is also possible to provide this machining from above onto the shaft diameter.

Furthermore, a dressing spindle 8 is provided, which carries a diamond wheel and is used to dress the grinding wheel 11. Furthermore, a device 14 for changing the grinding wheel 1 1 is shown. The grinding wheels are received in a holder in the manner of a magazine and are fed by means of the Umsetzungsroboters 15 from the magazine of the respective grinding spindle. The conversion robot 15 has a gripper unit 16, by means of which it removes the desired grinding wheel from the supply magazine as required and optionally a specific cooling nozzle set 17 belonging to the grinding wheel and feeds both into the region of the operative position of the grinding wheel on the workpiece. It is also possible that the cooling nozzle set 17 is gripped independently of the grinding wheel with the Umsetzungsroboter and is guided to the loop engagement point, which can be done during grinding.

In the rear area of the grinding machine, shown in Figure 1 above, a control cabinet 18 is provided, which includes the CNC control of the grinding machine, with which the grinding machine is controlled.

FIG. 2 shows a plan view of a grinding machine for carrying out the method according to the invention, which has a first wheelhead 5 and a second wheelhead 20. Only the basic structure of the grinding machine is shown in plan view. In this grinding center, a workpiece headstock 2 and a tailstock 3 are arranged on a machine stand 1. Between the workpiece headstock 2 and the tailstock 3, the clamping and rotation axis 4 is formed for the workpiece 10, which coincides with the longitudinal axis of the workpiece. Mounted on a workpiece spindle 2a of the workpiece headstock 2 (C-axis) is a chuck 6 which receives a centrically circumferential tip, not shown, and additionally has compensating jaws 6a (also not shown). These jaws clamp the workpiece firmly on its circumference. This chuck is intended above all to initiate larger drive torques in the workpiece. This is necessary, for example, at least when grinding the profile sections of the workpiece 10. In order to compensate for the runout with respect to the center formed by the clamping and rotation axis 4 as well as all other dimensional, shape and position tolerances at the clamping point, the clamping jaws 6a of Chuck 6 performed balancing. Such applications for chucks are already known in the art, so that the description of its mode of action is omitted here. A first cross slide, which is shown in Figure 2 on the left, is parallel, which is represented by the ZI axis in the form of a double arrow, and at right angles, which is shown in Figure 2 on the left by the X1 axis in the form of a double arrow, to Rotation axis 4 of the workpiece 10 CNC-controlled movable. The first cross slide carries a first wheelhead 5, to which a first grinding spindle 9 is attached with a first grinding wheel 11. Further CNC-controlled adjustment possibilities are given by the fact that there is a horizontal adjustment possibility for the workpiece longitudinal axis 4 (A1 axis) and an adjustment possibility via the CNC-controlled pivot axis (B1 axis) arranged vertically at right angles to the rotation axis 4 of the workpiece 10 , In the front region of Figure 2, the first grinding spindle 9 is shown mounted, which serves to receive the grinding wheel 1 1. On this grinding spindle 9, the grinding wheels 11 can be changed fully automatically programmatically by a grinding wheel changing device, not shown. To the grinding wheel must then be mitausverausch in a known manner, the appropriate coolant lubricant nozzle or the appropriate coolant nozzle set, which is not shown separately in Figure 2.

With the first wheel spindle 5 shown on the left in FIG. 2, the cylindrical diameters and the plane surfaces on the workpiece 10 are ground.

Furthermore, in FIG. 2, on the left side, axially parallel to the workpiece spindle 2 a (C axis), there is a dressing spindle 8, which serves with its diamond wheel to dress the first grinding wheel 11 of the first grinding headstock 5. The device for changing the grinding wheel 1 1 is not shown separately in Figure 2. The grinding wheels 11 of the first grinding headstock 5 are used for grinding the shaft parts or the cylindrical sections on the shaft part, d. H. All outer diameters for the cylindrical sections, conical sections and similar contours are ground with these grinding wheels.

2, a second cross slide is parallel on the right side, which is marked as a Z2 axis with a double arrow, and at right angles, which is also shown in Figure 2 as X2 axis with double arrow, to the axis of rotation 4 of the workpiece 10 CNC. controlled moveable. This second cross slide carries a vertically CNC-controlled movable (Y2 axis) second wheelhead 20, to which a grinding spindle 22 is attached with a second grinding wheel 21. Another CNC-controlled adjustment consists of a horizontal, to the axis of rotation 4 of the workpiece 10 arranged CNC-controlled pivot axis, which is shown in Figure 2 as the A2 axis. In the front region of the grinding machine according to FIG. 2, a grinding spindle is mounted which serves to receive the grinding wheel 21. On this grinding spindle 22 (see FIG. 4B), these grinding wheels can be changed fully automatically in a program-controlled manner by means of a grinding disk changing device (also not shown). To the second grinding wheel 21 is then - if it is necessary - mitausgetausch in a known manner the appropriate coolant lubricant nozzle or the appropriate cooling lubricant nozzle set, but this is also not shown separately. A second dressing device 23 for dressing the grinding wheel 21 for the grinding headstock 20 arranged on the right in FIG. 2 is provided in the front grinding machine on the right-hand machine side.

In the rear region of the grinding machine, the control cabinet, not shown in Figure 2 is arranged, which receives the complete electrical control of the machine.

For grinding, the respective workpieces 10 of the grinding machine are supplied in a manner known per se, for example via an internal loading portal or by means of a loading portal arranged above the grinding machine in the sense of loading or unloading or taken out of the machine.

The basic design of a grinding machine shown in FIGS. 1 and 2 serves to carry out the method according to the invention, because with this basic design of the grinding machine, the complete machining of the cylindrical sections, plan sides and profile sections can be realized in such a way that during processing or during processing the internal stresses released in the workpiece between grinding operations can be reduced or compensated so that subsequent grinding operations can always be carried out on a workpiece which is at least largely freed from internal stresses. The course of the method according to the invention will now be explained in detail with reference to the following figures.

FIG. 3 shows a partial plan view of a part of the grinding machine implementing the method according to the invention, in which the workpiece is clamped between points before the grinding of a steady rest seat is carried out. In FIG. 3, this complete machining of a workpiece 10 in the form of a shaft part is shown in principle. This shaft part is received between a workpiece headstock 2 with CNC-controlled C-axis and a tailstock 3 in a clamping between tips 2b, 3a. To the required Torque in the grinding operations, in particular for the grinding of the profile sections to apply, is on a shaft-side shaft end 10a a from the prior art already known per se, compensating and axially retractable chuck 6 on the workpiece spindle 2a mitaufgenommen. In the extended position of the chuck 6 or its clamping jaws 6a, this can be firmly clamped on the shaft-side shaft end 10a of the workpiece 10, so that very high radial torques are transmitted to the workpiece 10 during the grinding process. This will be required when grinding the profile sections 1 c in the form of groove or tooth geometries in most cases. According to the illustration in FIG. 3, the clamping jaws 6a of the chuck are applied to the clamping region of the workpiece, ie on the shank end of the shaft. Therefore, in such a tensioned state, the cylindrical outer contour of this shaft-side shaft end can not be ground. It is therefore necessary that, for grinding this clamping range, the clamping jaws 6a are released from the workpiece 10 and the chuck is withdrawn with its clamping jaws 6a. However, for grinding these cylindrical outer regions, the workpiece remains firmly clamped between the tips 2b, 3a. In this case, the entrainment of the workpiece 10 takes place to its rotation by the friction between the centering 2b on the chuck and the present in the workpiece 10 center, in which engages this centering 2b. On the side opposite the workpiece headstock a tailstock 3 is provided, which engages by preferably hydraulic actuation in the center of the centering tip 3a of the tailstock 3 side facing center. The tailstock tip 3a is movable in the axial direction of the workpiece, so that with appropriate formation of an axial pressure, the workpiece is held in a centered manner between the two centering 2b and 3a so that a rotational entrainment is ensured by the workpiece headstock 2.

The grinding of a steady seat 25 is now carried out in the manner shown in Figure 3 after peeling with obliquely annotated grinding wheel 11. After completion of this grinding operation of grinding the steady rest, the clamping of the workpiece 10 is released, so that the workpiece can relax and the inner Tensions are released. In addition, the chuck with its clamping jaws is released from the workpiece. In this state, the tailstock tip 3a is depressurized and is located in the center of the shaft part only. As a result, the workpiece is no longer firmly clamped, nevertheless its centered position relative to the clamping and rotation axis 4, ie the geometric longitudinal axis 4 of the workpiece, is maintained. A loss of accuracy can not occur, but the accuracy of the grinding result is increased by the fact that between the two successive grinding operations, the workpiece has a chance to relax, so that subsequent grinding operations on a relaxed, ie of internal stress in the

Essentially free workpiece can be ground.

In principle, it would also be conceivable to completely detach the tailstock tip 3a from the center for the tensioning; In such a case, however, care should be taken by, for example, an additional gripper or a further support that the workpiece is supported in this state. After the relaxation process has been performed, during which, of course, the grinding process is interrupted, a re-clamping of the workpiece, so that a subsequent grinding operation can follow.

FIG. 4A shows a partial plan view according to FIG. 3 during pre-grinding of the profile section in the form of a toothing or grooves with an engaged / supporting steady rest. The pre-grinding of the profile section 10c is effected by means of a galvanically coated grinding wheel 21. This is done in a conventional manner by interpolating method on the CNC-controlled axis or by means of the CNC-controlled axes. With regard to the accuracy to be achieved, the electroplated grinding wheels 21 are well suited for pre-grinding, above all because they can realize a very high machining volume per unit of time.

After this grinding operation as pre-grinding of the profile section 10c, the clamping of the workpiece to compensate for the internal stresses possibly present in the workpiece by grinding, in such a way that the jaws 6a of the chuck 6 solved and the tailstock 3a only depressurized in the center of the shaft part 10 persists. As a result, the workpiece is no longer firmly clamped, but retains its defined position, which is important in terms of accuracy for subsequent grinding operations. After relaxation of the workpiece 10, this is firmly clamped again in a known manner after the inner stresses in the workpiece have become free by releasing the clamping. The relaxation of the workpiece is preferably useful both after roughing and after the finish grinding of individual sections, at least as long as the complete machining on the workpiece has not been completed.

In FIG. 4 a, the workpiece 10 clamped between the tips 2 b and 3 a with the chuck 6 applied simultaneously with its clamping jaws 6 a is shown. The workpiece has a shank-side shaft end 10a, cylindrical portions 10b delimited by plan sides, and profile portions 10c. On a ground steady seat 25, a bezel 26 is employed for supporting the relatively long wave-shaped workpiece. The chuck 6 with the inner centering 2b is mounted on the workpiece spindle 2a of the workpiece spindle stock 2. If, as shown in FIG. 4A, the profile section 10c is ground by means of the grinding wheel 21, the clamping device 6 remains tensioned with its clamping jaws 6a on the shank end 10a of the shaft. In order to be able to grind the corresponding profile sections, the grinding wheel 21 can be delivered via its not shown grinding headstock and the grinding spindle 21 carrying the grinding spindle on the two axes X2 and Z2 corresponding to the geometric shape of the profile section.

On the tailstock 3, a pressure control 30 is shown, by means of which the axial pressure of the tailstock tip 3a on the arranged at the front end of the workpiece center is preselected in the CNC control adjustable. This axial pressure serves to secure the clamping forces during the grinding process. To relax the tailstock tip 3a is placed pressure-free in its associated center of the workpiece 10, thus made the workpiece stress-free with respect to its clamping.

FIG. 4B shows a partial view in the direction A of the workpiece, which corresponds to the grinding state according to FIG. 4A, during the grinding of its profile section.

The clamping situation illustrated in FIG. 4B corresponds to that according to FIG. 4A. According to this partial view, the workpiece 10 is being ground straight on the profile section 10c. The adjustment axes A2, Y2 and Z2 are represented by respective double arrows. The workpiece is shown in the foreground as being held between the tips 2b and 3a. The grinding wheel 21 for grinding the profile section 10c is shown behind the workpiece with respect to the plane of the drawing according to FIG. 4B and inclined with its grinding spindle 22 in such a way that the oblique straight grooves in the profile section 10c can be ground by a corresponding interpolating operation between the axes Z2 and C.

FIG. 4C now shows the grinding situation according to FIG. 4B relative to the sectional plane BB. On the workpiece 10, the profile section 10c is shown in the form of a toothing or circumferentially distributed a plurality of extending in the longitudinal direction of the workpiece grooves. The grinding wheel 21 is received by its grinding spindle 22 and can be pivoted into the helix angle of the oblique toothing in a CNC-controlled manner via the A2 axis. Schematically, the C, Y2 and X2 axes are also represented by respective double arrows. Depending on the requirement, a profile section can also be ground with curved grooves, as in screw rotors, using the method according to the invention. FIG. 5 shows a partial plan view according to FIG. 3 during finish grinding of the cylindrical sections and the plan sides of the workpiece according to the method according to the invention. The basic structure corresponds to that according to Figure 3, so that this basic structure is not carried out again here.

The basic principle is that during the grinding operation, the workpiece remains clamped, but after this the clamping is released, so that internal stresses can be released in the workpiece and a tension-free state of the workpiece can be ensured for subsequent grinding operations. The finish grinding of the relevant sections takes place in the version shown according to FIG. 5 according to the peeling grinding method with an inclined grinding wheel 1 1. It is also possible in principle for the grinding of these sections to take place even with an inclined grinding wheel 11 in such a way that multiple cuts have to be made. In this case, the cylindrical sections are ground in the inclined recess grinding process. After the cylindrical sections have been finished ground, the work piece 10, d. H. After this grinding operation, the clamping of the workpiece 10 is released to relax it, in such a way that the clamping jaws 6a of the chuck 6 is released and the tailstock tip 3a rests only in the center of the shaft part 10 without pressure. As a result, the workpiece is no longer tensioned, so that the internal stresses released or generated during grinding are released and, when re-sharpened, a machining state free of internal stresses is present for the workpiece.

FIG. 6 shows a side view of the area of the grinding machine in which the workpiece is clamped, namely during the grinding of the profile section 10 c according to the method according to the invention.

The basic structure and procedure during grinding or between individual grinding operations corresponds to those described above with particular reference to FIGS. 3 and 5, so that this basic structure will not be described again. According to Figure 6, the finish grinding of the profile section 10c takes place. The profile section 10c is formed in the present example as a helical toothing, wherein the grinding takes place with a galvanic or ceramic bonded grinding wheel 21. A ceramic bonded grinding wheel may preferably be used to finish the profile section 10c. The finish grinding takes place in a manner known per se by an interpolating method of the various CNC-controlled axes for the second grinding wheel 21. It is understood that to achieve a very high accuracy, the electroplated grinding wheels 21 have a very high accuracy for finished welding have to. In case of Use of ceramic bonded grinding wheels 21 are provided by dressing with the required profile. This latter operation is dispensable, provided that the required accuracy on the finished workpiece 10 can already be achieved by the previously described roughing process for the profile section. In such a case, the pre-grinding described in FIGS. 4A, B, C would be the finishing grinding operation. After the finish grinding operation of the profile section 10c is completed, the work clamping is released and the same is removed from the machine with a suitable handling system.

Finally, in FIG. 7, exemplary wave-like workpieces are drawn, which can be ground by the method according to the invention. These wave-shaped workpieces have cylindrical sections as well as profile sections. This is a transmission shaft 27a, another transmission shaft 27b, the latter having three profile sections, and two rotor shafts 28/29 for compressors, blower vacuum pumps or positive displacement pumps. It is clear from these wave-like components with profile sections given by way of example only that these components are highly complex ground surface designs, which moreover require very high production accuracy, because these shafts roll on one another with precisely matching wave crests and the respective flanks. If the illustrated shafts must be used for compressors or positive displacement pumps, the requirements are even higher, because in addition to the simple unrolling a sealing function in the profiles when combing two mutually manufactured such wellen is to ensure.

Surprisingly, it has now been found that the complete grinding machining of such relatively complicated wave-shaped workpieces does not require a single clamping, which is not released during the entire machining, in order to achieve improved dimensional, positional and shape accuracies.

LIST OF REFERENCE NUMBERS

1 machine stand

2 Workhead

2a workpiece spindle

2b Workpiece headstock tip

3 tailstock

3a tailstock tip

4 clamping and rotation axis

5 first wheelhead

6 chucks

6a clamping jaws

8 first dressing spindle

9 first grinding spindle

10 workpiece / shaft part

10a shank side shaft end

10b cylindrical section

10c profile section

11 first grinding wheel

12 pivot axis (A-axis)

13 pivot axis (B axis)

14 Device for changing the grinding wheel

15 conversion robots

16 gripper unit

17 cooling nozzle set

18 control cabinet

19 vertical guideways

20 second wheelhead

21 second grinding wheel

22 second grinding spindle

23 second dressing spindle

24 coolant / lubricant hoses

25 steady seat

26 bezel

27a gear shaft

27b gear shaft Rotor shaft for compressors, blowers, vacuum pumps, etc. Rotor shaft for positive displacement pumps

Andrücksteuerung

Claims

claims

Method for grinding at least one respective cylindrical section (10b) and profiled section (10c) having workpieces (10) on one and the same grinding machine (100), which has only one Werkstücksp indelstock (2) and a tailstock (3), wherein the cylindrical portion (10b) is ground with a first non-cylindrical grinding wheel (11), the workpiece (10) being ground in the grinding machine (100) in a first setting in a first grinding operation, characterized

that after the first grinding operation the first setting is released,

that subsequently a second set-up is produced,

the workpiece (10) is subsequently ground in a second grinding operation, and the profiled section (10c) is made by profile grinding with a second profiled grinding wheel (21).

A method according to claim 1, characterized in that in further grinding operations, the clamping respectively dissolved and then the workpiece (10) is stretched again before the subsequent grinding operation begins.

A method according to claim 2, characterized in that the first grinding wheel (11) is arranged on a first wheelhead (5).

A method according to claim 2 or 3, characterized in that the second grinding wheel (21) is arranged on a second wheelhead (20).

Method according to one of claims 1 to 4, characterized in that the workpiece (10) between the clamping and rotation axis (4) defining, in the end sides introduced centering holes engaging peaks (2b, 3a) is clamped, wherein one of the tips (3a ) is arranged in the tailstock (3) and in the first setting an axially directed pressure load on the workpiece (10) exerts, which is transferred to release the clamping in a non-pressurized state.

6. The method according to claim 5, characterized in that for releasing the clamping the tailstock tip (3a) moves along its Z-axis and out of engagement with the tailstock tip (3a) facing center hole of the workpiece (10) is brought.

7. The method according to claim 5 or 6, characterized in that the workpiece (10) in its clamping with an additional clamping device (6) which on the outer circumference of a cylindrical portion (10b) of the workpiece (10), in particular by means of clamping jaws (6a) , attacks, gets tense.

8. The method according to any one of claims 1 to 7, characterized in that in the first grinding operation at least one Lünettensitz (25) is ground, in the second grinding operation, the profiled section (10c) is pre-ground, in a third grinding operation, the cylindrical portion (10b ) and finished on the workpiece (10) flat surfaces are ground and finished in a fourth grinding operation of the profiled section (10c), wherein between all successive grinding operations, the clamping respectively dissolved and then the workpiece (10) is stretched again before the subsequent grinding operation begins ,

9. The method according to claim 8, characterized in that a bezel (26) for supporting the workpiece (10) to the steady seat (25) is delivered after it has been ground.

10. The method according to any one of claims 1 to 9, characterized in that the cylindrical portions (10b) by Längsschälschleifen or plunge grinding and the profiled portions (10c) are produced by profile grinding.